Global fixed-time trajectory tracking control of underactuated USV based on fixed-time extended state observer

This paper studies the trajectory tracking problem of unmanned surface vehicle subject to unmeasurable velocities and unknown disturbances. By combining a fixed-time extended state observer (FESO) and a fixed-time differentiator, a fixed-time sliding mode control (FTSMC) law is proposed, in which a saturation function is adopted to make the terminal sliding mode surface leave the singularity area. The value of this paper can be described: first, this paper designs a novel guidance law that can converge in a fixed time to reduce the convergence time of the error. Then, unmeasurable velocities and lumped disturbances are estimated by applying a FESO. Meanwhile, a fixed-time differentiator is used to obtain real-time differential signals, thus reducing the difficulty of controller design. Subsequently, a novel auxiliary dynamic system is designed to address actuator saturation. According to Lyapunov's theory, the entire closed-loop control system has uniformly global fixed-time stability (UGFTS). The superiority of the designed controller is demonstrated through numerical simulations. (c) 2022 ISA. Published by Elsevier Ltd. All rights reserved.

Automated summary

This paper addresses the trajectory tracking problem of unmanned surface vehicles in the presence of unmeasurable velocities and unknown disturbances. A fixed-time sliding mode control law is proposed by combining a fixed-time extended state observer and a fixed-time differentiator. The value of this paper lies in the design of a novel guidance law that converges in a fixed time, the estimation of unmeasurable velocities and lumped disturbances using a fixed-time extended state observer, and the use of a fixed-time differentiator to obtain real-time differential signals.